Bolt type seals are well known as single use seals and are widely used to secure hasps and latches on doors of freight containers and trailers. Openings in the hasp or latch are brought together as the door is locked. A bolt is passed through the openings and forced into a lock. Permanent numbers on the bolt and lock are recorded. The security of the bolt type seal may be visually observed and the numbers compared with recorded numbers. The lock and bolt may be checked by attempting to pull them apart, and twisting and looking for any unusual scratches or marks which may indicate attempts at vandalism or theft. Bolt type seals are used primarily where the loads may be stored for example overnight without direct supervision.
Such bolt type seals are identified by the American Society for Testing and Materials (ASTM) as Class 3 seals. Class 3 is defined as rigid bolt and bolt seals, including heavy duty metal padlock types. The ASTM further classifies such seals with letters according to compressive load requirements for cutting, loads for failure, torque or bending and impact force sustaining.
Fiber optic seals of the type used in the present invention have been described in the United States Pat. No. 4,729,626, 4,130,341, 4,106,849 and 4,074,415 by Lorin R. Stieff. While no particular classification exists for such type seals in the most recent ASTM designation F1158-88, it is believed that such seals might be classified in Group 2 with strap, cinch or non-scored seals.
The Group 3 seals are used in situations where vandalism or theft by forced entry by difficult-to-identify persons might be involved. The Group 2 seals are used in completely different situations in which the seals are primarily used to detect tampering and to ensure that the containers or housings, for example meter housings, have not been opened.
It would be unusual to use Group 2 and Group 3 seals concurrently. Group 2 seals would not ordinarily be used on freight containers or trailers, which are subjected to vibrations and rough treatment which would tend to tear or destroy the Group 2 strap-type seals.
A continued problem exists in how to detect tampering with seals, and that continuing problem has been specifically referred to in the ASTM Guide F1158-88 published in August 1988, which is available from the American Society for Testing and Materials, 1916 Ray Street, Philadelphia, Pa. 19103, which also publishes an annual book of ASTM standards, in which, in Volume 15.07, the following standards appear:
F832, Classification of Security Seals;
F883, Performance Specification for Padlocks;
F946, Guide for Establishing Security Seal Control and Accountability Procedures.
The present invention addresses improvements in seal security and accountability.